Bio chapter 2

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Atom

The smallest fundamental unit that retains the properties of the element or compound.

Element

One type of atom.

Atomic number

The number of protons in the nucleus of an atom. This number is given on the periodic table, above abbreviation symbol.

Atoms are composed of 3 fundamental particles. Name the particle, it's charge and location.

1. Proton, positive charge, located in the nucleus.

2. Neutron, neutral charge, located in the nucleus.

3. Electron, negative charge, located orbiting the nucleus.

Nucleus

The central part of the atom that houses the protons & neutrons.

Orbitals

The clouds surrounding the nucleus where the electrons exist.

What do electrons do?

Electrons are involved in all chemical reactions. They give an atom ormolecule it's unique chemical properties.

How do you find the Atomic Mass?

The atomic mass (A) is equal to the number of protons (Z) plus the number neutrons. The atomic mass (Z) number is written on the top left side of the symbol.

Atomic Number

The atomic number is found on the periodic table above the symbol. It is equal to the number of protons. It is written on the bottom left side of the symbol.

How do you find the number of neutrons in an atomic symbol?

You subtract the atomic number from the atomic mass. N = A - Z

Isotopes

Atoms with the same number of protons but a different number of neutrons.

Radioactivity

Certain isotopes are unstable & will spontaneously break down to form a more stable nucleus.

Ions

Atoms are electronically neutral unless the number of electrons does not equal the number of protons.

Chemical bond

A type of force that holds 2 or more atoms together.

Ionic Bond

An electron is taken from one atom by another atom. "electron stealing"

Ionic Bond = metal + non metal

Covalent Bond

ElectronsElectrons are shared between atoms. "electron sharing"

Covalent Bond = non metal + non metal

Electronegativity

A measure of how strongly an atom holds on to it's electrons.

Polar Covalent Bond

If 2 atoms in a covalent bond have significantly different electronegativity values, than a polar covalent bond is formed. (the difference should be between 0.5 to 1.7)

Hydrogen Bonds

Hydrogen bonds form when a hydrogen atom is directly bonded to an atone of nitrogen, oxygen or fluorine. Hydrogen bonds are a specific type of strong polar bonds.

van der Waals forces

A weak type of attraction between molecules. This occurs when the covalent bonds of a molecule have a electronegativity difference of less than 0.5 A hydrocarbon is a van der Waals force.

Heat storage / Heat capacity

Water conducts heat more effectively than air. (approx. 6 times more effectively)

Ice formation

As a solid, water is less dense than as a liquid. (ie: ice floats)

High heat of vaporization / High boiling point

Everyframe of water that evaporates from human skin takes heat away from the body, this is why we sweat when we are physically active.

Cohesion

Because of the abundant hydrogen bonding, water molecules stick together and at the surface of a body of water the molecules form a "skin". Cohesion occurs when molecules are attracted to other molecules of the same type.

Adhesion

Occurs when polar molecules are attracted to different polar molecules.

High polarity

Water is sometimes called the universal solvent because many substances will dissolve in it. Because water has a polar covalent bond, it will dissolve other molecules that also have a polar covalent bond.

Hydrophilic

Water-loving. Will dissolve in water. Polar covalent bonds and hydrogen bonds are hydrophilic.

Hydrophobic

Water + fear. Repels water. Will not dissolve in water. Van der Waals forces are hydrophobic.

Acid

Adding an acid to water will increase the number of H3O+ ions present. Acid has a pH below 7.

Base

Adding a base to water will increase the number of OH- ions present. The pH of a base is higher than 7.